The present invention relates to an electrical power supply system for an automotive vehicle with internal combustion engine equipped with an automatic stop and restart device for the internal combustion engine; the device often being designated as “Stop & Start” (S&S).
Automotive vehicles are using an increasing number of electrical devices. As examples we can mention S&S devices, power steering, climate control units or electric brakes.
The majority of these devices consume high electrical current during short times. It was therefore necessary to add to the traditional 12 volt battery one or more supplementary sources of electrical energy, in order to be able to supply the required electrical power and in order to avoid voltage drops in the onboard electrical network to which the various electricity consuming devices of the vehicle are connected.
One traditional solution consists in using as a supplementary energy source a second battery or one or more high power capacitors. These capacitors are usually called super capacitors and are designated by the term Ucap. These super capacitors are in general associated with DC/DC type converters in order to adapt their voltage to the supply voltage of the electrical devices that they feed.
Certain vehicles on the market are equipped with a voltage maintaining device, known under the abbreviation DMT, which is mounted in series or in parallel with the battery. The DMT consists of an additional energy source controlled by electronics, which facilitates the starts and avoids voltage drops in the onboard electrical network of the vehicle.
These solutions in fact pose complexity problems for the electrical architecture of the vehicle, resulting in increase of the vehicle mass, loss of available space under hood due to the space occupied by the DMT and reduction in performance of the devices not supplied by the converter.
As an example, we can mention patent FR 2902705 which relates mainly to a plurality of control strategies for a micro-hybrid system of an automotive vehicle, whereby all the intelligence necessary for controlling the micro-hybrid system is integrated in the system. The disadvantages of the proposed solution in FR 2902705 are, on the one hand, the use of a significant number of elementary cells (in general 2.5 V) of super capacitors and, on the other hand, the connection of the super capacitors to the electrical ground.
We can also mention patent EP 1034092 which relates to an electrical circuit of an automotive vehicle, whereby the circuit is equipped with a second source of electrical energy and with a plurality of relays. The described configuration is similar to the aforementioned patent FR 2902705: the super capacitor is charged with approximately the same voltage as the battery and is connected to the ground.